Polymer-based latex for cementing fluids

ABSTRACT

A cementing fluid composition includes a latex and a cement. The latex includes a first polymer and a second polymer. The first polymer includes polyvinyl alcohol and polyvinyl acetate. A molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%. The second polymer has a general structure in which x is an overall molar ratio of styrene, y is an overall molar ratio of butadiene, and z is an overall molar ratio of carboxylic acid. A sum of x, y, and z is represented as s. Styrene (x) is in a range of from about 20% to about 30% of s. Butadiene (y) is in a range of from about 70% to about 80% of s. Carboxylic acid (z) is in a range of from about 1% to about 5% of s.

TECHNICAL FIELD

This disclosure relates to cementing fluids.

BACKGROUND

Natural resources such as gas, oil, and water in a subterranean formation can be produced by drilling a wellbore into the subterranean formation while circulating a drilling fluid in the wellbore. A well is cemented prior to hydrocarbon production. Well cementing includes introducing cement to provide a hydraulic seal that establishes zone isolation, prevents fluid communication between producing zones in the borehole, and blocks the escape of fluids to the surface. Well cementing also anchors and supports tubulars installed in the wellbore and protects the tubulars against corrosion by formation fluids.

SUMMARY

This disclosure describes technologies relating to cementing fluids, and in particular, polymer-based latexes for use in cementing fluids. Certain aspects of the subject matter described can be implemented as a cementing fluid composition. The cementing fluid composition includes a latex and a cement. The latex includes a first polymer and a second polymer dispersed in water. The first polymer includes polyvinyl alcohol and polyvinyl acetate. A molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%. The second polymer is derived from styrene, butadiene, and a carboxylic acid. The second polymer has the general structure:

where x is an overall molar ratio of styrene in the second polymer, y is an overall molar ratio of butadiene in the second polymer, and z is an overall molar ratio of carboxylic acid in the second polymer. A sum of x, y, and z is represented as s. Styrene (x) is in a range of from about 20% to about 30% of s. Butadiene (y) is in a range of from about 70% to about 80% of s. Carboxylic acid (z) is in a range of from about 1% to about 5% of s. The cement includes calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and gypsum. A concentration of the cement in the cementing fluid composition is in a range of from about 50 weight percent (wt. %) to about 80 wt. %. A concentration of the latex in the cementing fluid composition is in a range of from about 1 wt. % to about 15 wt. %.

This, and other aspects, can include one or more of the following features. In some implementations, the cementing fluid composition includes an additive. The additive can include at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive. In some implementations, a molar ratio of the first polymer to the second polymer in the cementing fluid composition is about 1:1. In some implementations, the molar concentration of the polyvinyl alcohol in the first polymer is about 88%.

Certain aspects of the subject matter described can be implemented as a method. A first polymer is formed. The first polymer includes polyvinyl alcohol and polyvinyl acetate. Forming the first polymer includes mixing calcium hydroxide and water to form a first mixture. Forming the first polymer includes adding polyvinyl acetate to the first mixture to form a second mixture. Forming the first polymer includes stirring the second mixture for a first specified time duration sufficient to hydrolyze at least a portion of the polyvinyl acetate into polyvinyl alcohol and form the first polymer. A molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%. A second polymer is formed. Forming the second polymer includes mixing citric acid and water to form a third mixture. Forming the second polymer includes adding a styrene-butadiene polymer to the third mixture to form a fourth mixture. Forming the second polymer includes stirring the fourth mixture for a second specified time duration sufficient for carboxylation of the styrene-butadiene to occur and form the second polymer. The second polymer has the general structure:

where x is an overall molar ratio of styrene in the second polymer, y is an overall molar ratio of butadiene in the second polymer, and z is an overall molar ratio of carboxylic acid in the second polymer. A sum of x, y, and z is represented as s. Styrene (x) is in a range of from about 20% to about 30% of s. Butadiene (y) is in a range of from about 70% to about 80% of s. Carboxylic acid (z) is in a range of from about 1% to about 5% of s. The first polymer and the second polymer are mixed with a cement to form a cementing fluid.

This, and other aspects, can include one or more of the following features. The additive can include at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive. In some implementations, a molar ratio of the first polymer to the second polymer in the cementing fluid is about 1:1. In some implementations, a concentration of the cement in the cementing fluid is in range of from about 50 wt. % to about 80 wt. %. In some implementations, a combined concentration of the first polymer and the second polymer in the cementing fluid is in range of from about 1 wt. % to about 15 wt. %. In some implementations, the molar concentration of the polyvinyl alcohol in the first polymer is about 88%.

Certain aspects of the subject matter described can be implemented as a method. A cementing fluid is flowed through a tubular placed within a wellbore formed in a subterranean formation. The cementing fluid includes a cement and a latex. The latex includes a first polymer and a second polymer. The first polymer includes polyvinyl alcohol and polyvinyl acetate. A molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%. The second polymer is derived from styrene, butadiene, and a carboxylic acid. The second polymer has the general structure:

where x is an overall molar ratio of styrene in the second polymer, y is an overall molar ratio of butadiene in the second polymer, and z is an overall molar ratio of carboxylic acid in the second polymer. A sum of x, y, and z is represented as s. Styrene (x) is in a range of from about 20% to about 30% of s. Butadiene (y) is in a range of from about 70% to about 80% of s. Carboxylic acid (z) is in a range of from about 1% to about 5% of s. A displacement fluid is flowed through the tubular, thereby displacing the cementing fluid to at least partially fill an annular space defined between the tubular and the wellbore. The cementing fluid is allowed to harden in the annular space defined between the tubular and the wellbore, thereby cementing the tubular in the wellbore.

This, and other aspects, can include one or more of the following features. The cement can include calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and gypsum. In some implementations, a concentration of the cement in the cementing fluid is in a range of from about 50 wt. % to about 80 wt. %. In some implementations, a concentration of the latex in the cementing fluid is in a range of from about 1 wt. % to about 15 wt. %. In some implementations, the cementing fluid includes an additive. The additive can include at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive. In some implementations, a molar ratio of the first polymer to the second polymer in the cementing fluid is about 1:1. In some implementations, the molar concentration of the polyvinyl alcohol in the first polymer is about 88%.

The details of one or more implementations of the subject matter of this disclosure are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of an example wellbore being drilled in a subterranean formation.

FIG. 2A is an infrared spectrum of an example polymer that can be included in a latex for a cementing fluid.

FIG. 2B is a plot showing a thickening time for the polymer whose infrared spectrum is shown in FIG. 2A.

FIG. 2C is a plot showing a thickening time for an example polymer that can be included in a latex for a cementing fluid.

FIG. 2D is an infrared spectrum of an example polymer that can be included in a latex for a cementing fluid.

FIG. 2E shows infrared spectra of example polymers that can be included in a latex for a cementing fluid.

FIG. 2F shows absorbance spectra of example polymers that can be included in a latex for a cementing fluid.

FIG. 2G is a proton nuclear magnetic resonance (1H NMR) spectrum of an example polymer that can be included in a latex for a cementing fluid.

FIG. 2H is a 1H NMR spectrum of an example polymer that can be included in a latex for a cementing fluid.

FIG. 2I shows infrared spectra of example polymers that can be included in a latex for a cementing fluid.

FIG. 2J is a bar graph showing zeta potentials of an example polymer that can be included in a latex for a cementing fluid prior to treatment and after treatment.

FIG. 2K is an infrared spectrum of the polymer whose infrared spectrum is shown in FIG. 2D after treatment.

FIG. 2L is a bar graph showing fluid loss control of various example drilling fluids including a latex.

FIG. 2M is a bar graph showing fluid loss control of various example drilling fluids.

FIG. 2N is a plot showing a thickening time for an example polymer that can be included in a latex for a cementing fluid.

FIG. 2O shows differential scanning calorimetry (DSC) thermograms of example polymers that can be included in a latex for a cementing fluid.

FIG. 2P shows thermogravimetric analysis (TGA) thermograms of a example polymers that can be included in a latex for a cementing fluid.

FIG. 3A is a schematic diagram of an example polymer that can be included in a latex for a cementing fluid.

FIG. 3B is an infrared spectrum of an example polymer that can be included in a latex for a cementing fluid, prior to hydrolysis.

FIG. 3C is an infrared spectrum of an example polymer that can be included in a latex for a cementing fluid, following hydrolysis.

FIG. 3D is a plot showing a thickening time for an example polymer that can be included in a latex for a cementing fluid.

FIG. 3E is a plot showing a thickening time for an example polymer that can be included in a latex for a cementing fluid.

FIG. 4 is a flow chart of an example method of forming a cementing fluid that includes a polymer-based latex.

FIG. 5 is a flow chart of an example method of cementing a wellbore in a subterranean formation.

DETAILED DESCRIPTION

This disclosure describes polymer-based latexes for use in cementing fluids. A polymer-based latex is a stable, aqueous colloidal dispersion of polymer particles. In some implementations, the polymer particles have an average particle diameter in a range of from about 10 nanometers (nm) to about 1,000 nm. A polymer-based latex can include additional components, such as monomers, oligomers, surfactants, viscosifiers, weighting agents, and other additives.

The subject matter described in this disclosure can be implemented in particular implementations, so as to realize one or more of the following advantages. The polymer-based latexes described can be included in cementing fluids to reduce and/or eliminate the potential of fluid channeling. The polymer-based latexes described can be included in cementing fluids to form thin-film barriers which can reduce and/or eliminate the potential of formation of micro-annuli. The polymer-based latexes described can be included in cementing fluids to form the thin-film barriers to reduce and/or eliminate filtration losses. The polymer-based latexes described can be included in cementing fluids to improve viscosity of the cementing fluids. The polymer-based latexes described can be included in cementing fluids to improve subsequent well performance and production. The polymer-based latexes described can reduce and/or eliminate fluid losses, which can minimize gas migration, improve wellbore integrity, and aid in the mixing ability of cement slurries.

FIG. 1 is a partial schematic perspective view of an example rig system 100 for drilling and producing a well. The well can extend from the surface through the Earth to one or more subterranean zones of interest. The example rig system 100 includes a drill floor 102 positioned above the surface, a wellhead 104, a drill string assembly 106 supported by the rig structure, and a fluid circulation system 108 to filter used drilling fluid from the wellbore and provide clean drilling fluid to the drill string assembly 106. For example, the example rig system 100 of FIG. 1 is shown as a drill rig capable of performing a drilling operation with the rig system 100 supporting the drill string assembly 106 over a wellbore. The wellhead 104 can be used to support casing or other well components or equipment into the wellbore of the well. The example wellhead assembly 104 can take a variety of forms and include a number of different components. For example, the wellhead assembly 104 can include additional or different components than the example shown in FIG. 1 . Similarly, the circulation system 108 can include additional or different components than the example shown in FIG. 1 .

The derrick or mast is a support framework mounted on the drill floor 102 and positioned over the wellbore to support the components of the drill string assembly 106 during drilling operations. A crown block 112 forms a longitudinally-fixed top of the derrick, and connects to a travelling block 114 with a drilling line including a set of wire ropes or cables. The crown block 112 and the travelling block 114 support the drill string assembly 106 via a swivel 116, a kelly 118, or a top drive system (not shown). Longitudinal movement of the travelling block 114 relative to the crown block 112 of the drill string assembly 106 acts to move the drill string assembly 106 longitudinally upward and downward. The swivel 116, connected to and hung by the travelling block 114 and a rotary hook, allows free rotation of the drill string assembly 106 and provides a connection to a kelly hose 120, which is a hose that flows drilling fluid from a drilling fluid supply of the circulation system 108 to the drill string assembly 106. A standpipe 122 mounted on the drill floor 102 guides at least a portion of the kelly hose 120 to a location proximate to the drill string assembly 106. The kelly 118 is a hexagonal device suspended from the swivel 116 and connected to a longitudinal top of the drill string assembly 106, and the kelly 118 turns with the drill string assembly 106 as the rotary table 142 of the drill string assembly turns.

In the example rig system 100 of FIG. 1 , the drill string assembly 106 is made up of drill pipes with a drill bit (not shown) at a longitudinally bottom end of the drill string. The drill pipe can include hollow steel piping, and the drill bit can include cutting tools, such as blades, discs, rollers, cutters, or a combination of these, to cut into the formation and form the wellbore. The drill bit rotates and penetrates through rock formations below the surface under the combined effect of axial load and rotation of the drill string assembly 106. In some implementations, the kelly 118 and swivel 116 can be replaced by a top drive that allows the drill string assembly 106 to spin and drill. The wellhead assembly 104 can also include a drawworks 124 and a deadline anchor 126, where the drawworks 124 includes a winch that acts as a hoisting system to reel the drilling line in and out to raise and lower the drill string assembly 106 by a fast line 125. The deadline anchor 126 fixes the drilling line opposite the drawworks 124 by a deadline 127, and can measure the suspended load (or hook load) on the rotary hook. The weight on bit (WOB) can be measured when the drill bit is at the bottom the wellbore. The wellhead assembly 104 also includes a blowout preventer 150 positioned at the surface 101 of the well and below (but often connected to) the drill floor 102. The blowout preventer 150 acts to prevent well blowouts caused by formation fluid entering the wellbore, displacing drilling fluid, and flowing to the surface at a pressure greater than atmospheric pressure. The blowout preventer 150 can close around (and in some instances, through) the drill string assembly 106 and seal off the space between the drill string and the wellbore wall. The blowout preventer 150 is a valve (or assembly of valves) at the top of the well that can be closed to seal the well to prevent a blowout, which is an uncontrolled release of formation fluid from the well.

During a drilling operation of the well, the circulation system 108 circulates drilling fluid from the wellbore to the drill string assembly 106, filters used drilling fluid from the wellbore, and provides clean drilling fluid to the drill string assembly 106. The example circulation system 108 includes a fluid pump 130 that fluidly connects to and provides drilling fluid to drill string assembly 106 via the kelly hose 120 and the standpipe 122. The circulation system 108 also includes a flow-out line 132, a shale shaker 134, a settling pit 136, and a suction pit 138. In a drilling operation, the circulation system 108 pumps drilling fluid from the surface, through the drill string assembly 106, out the drill bit and back up the annulus of the wellbore, where the annulus is the space between the drill pipe and the formation or casing. The density of the drilling fluid is intended to be greater than the formation pressures to prevent formation fluids from entering the annulus and flowing to the surface and less than the mechanical strength of the formation, as a greater density may fracture the formation, thereby creating a path for the drilling fluid to go into the formation. Apart from well control, drilling fluid can also cool the drill bit and lift rock cuttings from the drilled formation up the annulus and to the surface to be filtered out and treated before it is pumped down the drill string assembly 106 again. The drilling fluid returns in the annulus with rock cuttings and flows out to the flow-out line 132, which connects to and provides the fluid to the shale shaker 134. The flow line is an inclined pipe that directs the drilling fluid from the annulus to the shale shaker 134. The shale shaker 134 includes a mesh-like surface to separate the coarse rock cuttings from the drilling fluid, and finer rock cuttings and drilling fluid then go through the settling pit 136 to the suction pit 136. The circulation system 108 includes a mud hopper 140 into which materials (for example, to provide dispersion, rapid hydration, and uniform mixing) can be introduced to the circulation system 108. The fluid pump 130 cycles the drilling fluid up the standpipe 122 through the swivel 116 and back into the drill string assembly 106 to go back into the well.

Once the well has been drilled and tubulars are installed within the well, the rig system 100 can be used to cement the well. The circulation system 108 or another similar system can be used to flow a cementing fluid 109 into the well. The circulation system 108 or another similar system can be used to flow a displacement fluid into the well, which displaces the cementing fluid 109 to at least partially fill an annulus defined between the tubulars and the wellbore. The cementing fluid 109 is allowed to set (harden) to complete the well cementing process.

The cementing fluid 109 includes cement. The cement can include calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and gypsum. In some implementations, a concentration of the cement in the cementing fluid 109 is in a range of from about 50 weight percent (wt. %) to about 80 wt. %. Table 1 provides a general composition of an example cement.

TABLE 1 Generalized composition of example cement Compound Molar Concentration SiO2 23.2% Al2O3  3.7% Fe2O3  4.8% CaO 63.8% MgO  1.3% SO3  2.2% Alkalis 0.47% Lime 0.74% The cement can include, for example, tricalcium silicate, dicalcium silicate, tricalcium aluminate, calcium aluminoferrite, gypsum, magnesia, calcium oxide, and calcium hydroxide.

The cementing fluid 109 includes a latex, which is a polymer dispersed in water. The cementing fluid 109 is based on emulsion polymerization. In some implementations, the cementing fluid 109 includes a first polymer 109 a dispersed in water. The first polymer 109 a includes polyvinyl alcohol and polyvinyl acetate. In some implementations, the first polymer 109 a is a partially hydrolyzed polyvinyl acetate. In some implementations, a molar concentration of the polyvinyl alcohol in the first polymer 109 a is greater than 80% and less than 100%. For example, the molar concentration of the polyvinyl alcohol in the first polymer 109 a is in a range of from about 80% to about 90%, from about 85% to about 95%, or from about 85% to about 90%. For example, the molar concentration of the polyvinyl alcohol in the first polymer 109 a is about 88%.

In some implementations, the cementing fluid 109 includes a second polymer 109 b dispersed in water. The second polymer 109 b is derived from styrene, butadiene, and a carboxylic acid (for example, acrylic acid or methacrylic acid). In some implementations, the second polymer 109 b has the following general structure:

where x is an overall molar ratio of styrene in the second polymer 109 b, y is an overall molar ratio of butadiene in the second polymer 109 b, and z is an overall molar ratio of carboxylic acid in the second polymer 109 b. A sum of x, y, and z can be represented as s. In some implementations, x (styrene) is in a range of from about 20% to about 30% of s. In some implementations, y (butadiene) is in a range of from about 70% to about 80% of s. In some implementations, z (carboxylic acid) is in a range of from about 1% to about 5% of s. In some implementations, a ratio of x (styrene) toy (butadiene) is in a range of from about 0.22:1 to about 1:0.22.

In some implementations, the cementing fluid 109 includes both the first polymer 109 a and the second polymer 109 b. In some implementations, a molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 is in a range of from about 1:2 to about 2:1. For example, the molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 is about 1:1. In some implementations, a combined concentration of the first polymer 109 a and the second polymer 109 b in the cementing fluid 109 is in a range of from about 1 wt. % to about 15 wt. %. The cementing fluid 109 can include additional components, such as additives. Some non-limiting examples of additives that can be included in the cementing fluid 109 (either individually or in combination) include starch, cellulosic polymer, dispersant, set retarder, silica, or an expanding additive.

In some implementations, during cement hydration, the hydrophilic portion(s) of the first polymer 109 a, the second polymer 109 b, or both are attracted to the water while the hydrophobic portion(s) are directed to the air phase or to pores and capillaries not filled with water. As the water content is reduced, the hydrophobic portion(s) can coalesce together and form a film barrier. In some implementations, the first polymer 109 a, the second polymer 109 b, or both interact with cement hydration products to form a semi-permeable membrane.

Anhydrous cement compounds have a large number of oxygen ions. Hydrogen bonding between groups of the organic compounds can generate layers that can be adsorbed (by hydrogen bonding with the oxygen ions) onto the crystals of the anhydrous cement. At large potentials of hydrogen (pH), organic compounds (such as organic acid) are present in carboxylate form during cement hydration. Because cement crystals generally have a positive charge due to the presence of excess partial valences from calcium ions, the organic acids can react with the positive ions resulting in ionic bonding, followed by cross-linking for setting the cement.

FIG. 2A is an infrared spectrum of an example polymer that can be included in a latex for the cementing fluid 109. The infrared spectrum shown in FIG. 2A was obtained using a Varian Fourier transform infrared (FTIR) spectrophotometer equipped with a mercury cadmium telluride (MCT) detector and Golden gate accessory with an average of 128 scans at a resolution of 4 per centimeter (cm⁻¹). The example polymer whose infrared spectrum is shown in FIG. 2A was a carboxylated styrene butadiene polymer (for example, an implementation of the second polymer 109 b) that was dried at about 105 degrees Celsius (° C.) for about 2 hours to remove water content. The infrared spectrum (in percent reflectance) shown in FIG. 2A shows the presence of a carboxyl group at wavenumber 1640 inverse centimeters (cm⁻¹). The largest peak of the infrared spectrum shown in FIG. 2A corresponds to the oxygen-hydrogen bond (hydroxyl group) vibration at wavenumber 3367 cm⁻¹.

FIG. 2B is a plot showing thickening time for the implementation of the second polymer 109 b of FIG. 2A. Consistency of the cementing fluid 109 including the second polymer 109 b was measured as Bearden consistency (Bc) units on a scale from 1 to 100, where 100 is complete setting/hardening (no flow). Thickening time tests were performed at a borehole static temperature (BHST) of 154 degrees Fahrenheit (° F.), a borehole circulating temperature (BHCT) of 130° F., under pressure, and dynamic conditions to simulate pumping. A thickening time result of 9 Bc at 4 hours indicated a liquid state. Tables 2, 3, and 4 provide compositions of various implementations of the cementing fluid 109 and a control cementing fluid without a polymer-based latex and summarized performance results.

TABLE 2 Performance of control cementing fluid without latex Additive Quantity (grams) Water 245 Fluid loss additive 3.15 Retarder 6 Cement 779 Fluid loss at BHST 465 ml

TABLE 3 Performance of cementing fluid including 53 g of latex Additive Quantity (grams) Water 245 Fluid loss additive 3.15 Retarder 6 Second polymer 109b latex 53 Cement 779 Fluid loss at BHST 268.55 ml Thickening time at BHCT 9 Bc @ 4:28 hours

TABLE 4 Performance of cementing fluid including 105 g of latex Additive Quantity (grams) Water 245 Fluid loss additive 3.15 Retarder 6 Second polymer 109b latex 105 Cement 779 Fluid loss at BHST 41 ml

FIG. 2C is a plot showing thickening time for an implementation of the second polymer 109 b that exhibited premature setting and is unlikely to be suitable for inclusion in the cementing fluid 109. As shown in the plot of FIG. 2C, the polymer set (hardened) within 20 minutes, which can be considered too soon for cementing applications. The polymer can be treated (for example, by acid treatment) to make it more suitable for inclusion in the cementing fluid 109.

FIG. 2D is an infrared spectrum of the example polymer of FIG. 2C. The infrared spectrum shown in FIG. 2D was also obtained using the Varian FTIR spectrophotometer. The example polymer whose infrared spectrum is shown in FIG. 2D was a carboxylated styrene butadiene polymer (for example, an implementation of the second polymer 109 b). The infrared spectrum (in percent reflectance) shown in FIG. 2D also shows the presence of the carboxyl group, the hydroxyl group, and mono-substituted aromatics at peaks 696 cm⁻¹ and 3026 cm⁻¹. The rheological properties of the example polymer of FIG. 2C were also measured, and the results of the rheology measurements are provided in Table 5.

TABLE 5 Rheology of cement including second polymer 109b Rheology Room Temperature 120 °F RPM Up Down Up Down  3 11 10 13 18  6 12 11 14 20 100 19 20 26 25 200 31 31 35 35 300 41 41 48 48 600 71 71 76 76 10 second gel 12 16 10 minute gel 14 130 

FIG. 2E shows infrared spectra in percent transmittance of the example polymers of FIGS. 2A and 2D. FIG. 2F shows absorbance spectra of the example polymers of FIGS. 2A and 2D. The infrared spectra shown in FIG. 2E and the absorbance spectra shown in FIG. 2F were also obtained using the Varian FTIR spectrophotometer and provide a comparison of the locations of polystyrene and polybutadiene in the example polymers. The infrared spectra shown in FIG. 2E and the absorbance spectra shown in FIG. 2F reveal that the example polymer of FIG. 2A included slightly more butadiene and styrene in comparison to the example polymer of FIG. 2D.

FIG. 2G is a proton nuclear magnetic resonance (1H NMR) spectrum of the example polymer of FIG. 2A. The 1H NMR spectrum shown in FIG. 2G was obtained using an NMR spectrometer applying NMR with respect to hydrogen-1 nuclei within the molecules of the polymer in order to determine the structure of the polymer. A solvent (DMSO) was used to reveal the hydrogen-1 nuclei from the polymer. The 1H NMR spectrum shown in FIG. 2G shows a peak in the 0.8-1.2 parts per million (ppm) range for butadiene and a peak in the 6.5-8 ppm range for styrene. The example polymer of FIG. 2A had a ratio of butadiene to styrene in the polymer of 1:0.53.

FIG. 2H is a 1H NMR spectrum of the example polymer of FIG. 2D. The 1H NMR spectrum shown in FIG. 2H was also obtained using the NMR spectrometer. A solvent (DMSO) was used to reveal the hydrogen-1 nuclei from the polymer. The 1H NMR spectrum shown in FIG. 2H shows a peak in the 0.8-1.2 ppm range for butadiene and a peak in the 6.5-8 ppm range for styrene. The example polymer of FIG. 2D had a ratio of butadiene to styrene in the polymer of 1:0.22.

As mentioned previously, the second polymer 109 b can be treated with an acid treatment to reduce the anionic charge of the second polymer 109 b and render the second polymer 109 b less deprotonated in a basic solution. The acid treatment can include, for example, addition of citric acid to the second polymer 109 b. The addition of citric acid can also hinder the interaction of the second polymer 109 b with the positive cations (for example, calcium ions) of the cement, thereby delaying the setting/hardening of the cementing fluid 109 and preventing premature setting/hardening of the cementing fluid 109. FIG. 2I shows infrared spectra of example polymers that can be included in a latex for the cementing fluid 109 and can be treated with the acid treatment. All of the example polymers whose infrared spectra are shown in FIG. 2I are anionic polymers because of the presence of carboxyl groups in their structures.

FIG. 2J is a bar graph showing zeta potentials of an implementation of the second polymer 109 b prior to acid treatment and after acid treatment. As shown in FIG. 2J, the zeta potential decreased in magnitude due to the citric acid treatment. This confirmed that the citric acid treatment reduced the pH of the second polymer 109 b, making it less anionic and preventing it from prematurely setting/hardening in the cementing fluid 109. Table 6 shows pH measurements and thickening times for varying additions of citric acid to the second polymer 109 b. For each of the formulations in Table 6, the quantity of the second polymer 109 b was 26.5 grams.

TABLE 6 Effect of citric acid treatment on second polymer 109b Citric acid addition (grams) pH Thickening time 0 9.6 Gelled 0.5 3.5 Liquid - 22 Bc at 6 hours 1 2.92 1.5 2.68 2 2.46 2.5 2.31 3 2.18 3.5 2.07 4 2.03 5.25 1.61

FIG. 2K is an infrared spectrum of the implementation of the second polymer 109 b after acid treatment. In comparison to the infrared spectrum shown in FIG. 2D (prior to acid treatment), the infrared spectrum shown in FIG. 2K exhibits an increase in peak width corresponding to the hydroxyl group. Further, there is an additional smaller peak corresponding to the carboxyl group due to the addition of the citric acid. Acid treating the second polymer 109 b extended the thickening time of the cementing fluid 109 to beyond 6 hours, which can be considered sufficient time to perform cementing operations in hydrocarbon wells. Acid treating the second polymer 109 b also improves its ability to form a film barrier, which reduces filtration by reducing the deprotonation of the second polymer 109 b in a basic solution due to the reduced interaction with calcium ions of the cement.

FIG. 2L is a bar graph showing fluid loss control of various example cementing fluids. The first cementing fluid was a control fluid without a polymer-based latex. The second cementing fluid was a cementing fluid including an implementation of the second polymer 109 b (styrene-butadiene latex). The third cementing fluid was a cementing fluid including an implementation of the second polymer 109 b (styrene-butadiene latex). The fourth cementing fluid was a cementing fluid including an implementation of the second polymer 109 b (styrene-butadiene latex) that was treated with 1.5 grams (g) of citric acid. The fifth cementing fluid was a cementing fluid including an implementation of the second polymer 109 b (styrene-butadiene latex) that was treated with 5.25 g of citric acid. As shown in FIG. 2L, the first cementing fluid (control without latex) exhibited the most fluid loss (worst ability for fluid loss control), while the fifth cementing fluid (treated with the most citric acid) exhibited the least fluid loss (best ability for fluid loss control).

FIG. 2M is a bar graph showing fluid loss control of various example cementing fluids. The first cementing fluid was a control fluid without a polymer-based latex. The second cementing fluid was a cementing fluid including 53 grams of an implementation of the second polymer 109 b (styrene-butadiene latex). The third cementing fluid was a cementing fluid including 105 grams of the same implementation of the second polymer 109 b (styrene-butadiene latex) as the second cementing fluid. The fourth cementing fluid was a cementing fluid including 53 grams of an implementation of the second polymer 109 b (styrene-butadiene latex) that was treated with 1.5 g of citric acid. As shown in FIG. 2M the first cementing fluid (control without latex) exhibited the most fluid loss (worst ability for fluid loss control), while the fourth cementing fluid (treated with citric acid) exhibited the least fluid loss (best ability for fluid loss control). Increasing the concentration of the second polymer 109 b in the cementing fluid also appeared to improve the fluid loss control of the cementing fluid.

FIG. 2N is a plot showing a thickening time for an implementation of the second polymer 109 b that was citric acid treated to be included in the cementing fluid 109. The thickening time was considered sufficient for application in cementing operations of hydrocarbon wells. The composition and experiment results are summarized in Table 7.

TABLE 7 Cementing fluid including second polymer 109b treated with citric acid Additive Quantity (grams) Water 245 Citric acid 3 Second polymer 109b 53 Fluid loss additive 1.16 Dispersant 1.94 Low temperature retarder 5.45 Mid temperature retarder 5.45 Silica sand 272.65 Expansion additive 7.79 Cement 779 Fluid loss at BHST 128 mL Thickening Time at BHCT 34 Bc at 4 hours and 45 minutes Settling No Free water 0

FIG. 2O shows differential scanning calorimetry (DSC) thermograms of the example polymers of FIGS. 2A and 2D. The DSC thermograms shown in FIG. 2O were obtained using a differential scanning calorimeter (DSC Q20), which was coupled to a refrigerated cooling system. The differential scanning calorimeter scanned running at a heating rate of 20 degrees Celsius per minute (° C./min) under a nitrogen purge rate of 20 cubic centimeters per minute (cm³/min) between room temperature to 200° C. The DSC thermograms were obtained from a second heating process (after cooling) at a heating rate of 20° C./min. The example polymer of FIG. 2A exhibited a glass transition temperature of −1.21° C., while the example polymer of FIG. 2D exhibited a glass transition temperature of 7.86° C. The lower glass transition temperature of the example polymer of FIG. 2A may be attributed to the greater content of butadiene present in the example polymer of FIG. 2A in comparison to the example polymer of FIG. 2D.

FIG. 2P shows thermogravimetric analysis (TGA) thermograms of the implementations of the second polymer 109 b of FIGS. 2A and 2D. The TGA thermograms shown in FIG. 2P were obtained using a thermal gravimetric analyzer (TGA Q500) that was programmed to provide a heating rate of 10° C./min between 25° C. to 900° C. at atmospheric pressure to determine weight loss of a sample over a specified temperature range. Both example polymers of FIGS. 2A and 2D experienced a weight loss of about 50% at a decomposition temperature range of 25-250° C. due to the presence of water and other additives. For a decomposition temperature range of 250-600° C., the example polymer of FIG. 2A experienced the hottest decomposition temperature of 438° C., while the example polymer of FIG. 2D experienced the hottest decomposition temperature of 425° C. It is generally known that polybutadiene decomposes at a hotter temperature in comparison to polystyrene. In comparison to the example polymer of FIG. 2D, the example polymer of FIG. 2A exhibited taller peaks for polybutadiene and polystyrene. Table 8 provides a summary of results of the TGA and DSC analyses.

TGA Analysis Air atmosphere Nitrogen atmosphere Label 2A 2B 2A 2B Volatiles (wt. %) 50.1 49.4 50.1 48.8 SBR (wt. %) 49.3 49.3 49.3 49.6 Residue (wt. %) 0.6 1.3 0.4 1.1 T_(max) (° C.) 438.1 425.5 438.1 425.5

TABLE 8 Summary of TGA and DSC analyses for example polymers of FIGS. 2A and 2D DSC Analysis T_(start) (° C.) −8.4 0.2 T_(mid) (° C.) −1.2 7.9 T_(end) (° C.) 5.9 14

The potential of hydrogen (pH) was measured for each of the implementations of the second polymer 109 b of FIGS. 2A and 2D. The pH can have an effect on the interaction of the second polymer 109 b with the cement in the cementing fluid 109. In a pH range of 3.5-6, deprotonation of additives (such as sulphonated initiator and emulsifier) begins as the methacrylic acid is fully protonated. At a pH of greater than 6 and up to 9, deprotonation of the methacrylic acid begins and results in a relatively increased negative surface charge. At a pH of 9, there is a sudden increase in negative surface change, indicative of complete deprotonation. At a pH of greater than 9, there is a slight increase in negative surface charge due to the presence of greater ionic strength in the aqueous phase. The pH of the example polymer of FIG. 2A (pH 6.5) was less than the pH of the example polymer of FIG. 2D (pH 9.7). Therefore, the example polymer of FIG. 2D exhibited a greater level of deprotonation in comparison to the example polymer of FIG. 2A. In order to confirm the greater anionic charge due to the higher pH and higher deprotonation of the example polymer of FIG. 2D, zeta potential measurements were conducted. The results of the zeta potential measurements are summarized in Table 9. As shown in Table 9, the zeta potential of the example polymer of FIG. 2D was greater than the zeta potential of the example polymer of FIG. 2A, which confirms the pH readings.

TABLE 9 Zeta potential measurements for example polymers of FIGS. 2A and 2D Test Number Polymer 2A Polymer 2D 1 −26.31 −41.23 2 −25.08 −40.27 3 −20.6 −36.33 4 −20.08 −32.29 5 −19.74 −33.13

FIG. 3A is a schematic diagram of an example polymer that can be included in a latex for the cementing fluid 109. The example polymer shown in FIG. 3A is an implementation of the first polymer 109 a including polyvinyl acetate and polyvinyl alcohol. The example polymer shown in FIG. 3A can be polyvinyl acetate that has been partially hydrolyzed, such that at least a portion of the acyl groups (R—C═O) and/or alkoxy groups (R—O) have been converted to alcohol groups (R—OH). The presence of hydroxyl groups (—OH) in the first polymer 109 a allows for adequate mixing and sufficient hydrogen bonding in the cementing fluid 109 for appropriate fluid loss control. Calcium hydroxide (lime) can be used to partially hydrolyze the polyvinyl acetate. In base-catalyzed hydrolysis, electron-withdrawing substituents in acyl groups and/or alkoxy groups facilitate the hydrolysis.

FIG. 3B is an infrared spectrum of an implementation of the first polymer 109 a prior to hydrolysis. FIG. 3C is an infrared spectrum of an implementation of the first polymer 109 a after hydrolysis. The infrared spectra (in percent reflectance) shown in FIGS. 3B and 3C were also obtained using the Varian FTIR spectrophotometer. The infrared spectra shown in FIGS. 3B and 3C show an increase in width of the hydroxyl group peak from before hydrolysis (FIG. 3B) to after hydrolysis (FIG. 3C), indicating an increase in the conversion of acetate into alcohol. In turn, the infrared spectra shown in FIGS. 3B and 3C also show a decrease in the acetate peak from before hydrolysis (FIG. 3B) to after hydrolysis (FIG. 3C), which affirms the conversion of acetate into alcohol as a result of the hydrolysis.

FIG. 3D is a plot showing thickening time for an example polymer that can be included in a latex for the cementing fluid 109. Thickening time tests were performed at a BHST of 154° F., a BHCT of 130° F., under pressure, and dynamic conditions to simulate pumping. Table 10 provides the composition of the implementation of the cementing fluid 109 including the first polymer 109 a and summarized performance results. The fluid loss testing exhibit excellent fluid loss control (32 mL/30 min) as well as an acceptable thickening time for the application of cementing operations for hydrocarbon wells.

TABLE 10 Cementing fluid including first polymer 109a Additive Quantity (grams) Water 245 Lime 3 First polymer 109a 54 Fluid loss additive 1.16 Dispersant 3.89 Low temperature retarder 11.6 Cement 779 Fluid loss at BHST 32 mL Thickening Time at BHCT 16 Bc at 5 hours and 25 minutes Settling No Free water 0

FIG. 3E is a plot showing thickening time for an example polymer that can be included in a latex for the cementing fluid 109. Thickening time tests were performed at a BHST of 181° F., a BHCT of 181° F., under pressure, and dynamic conditions to simulate pumping. Table 11 provides the composition of the implementation of the cementing fluid 109 including the first polymer 109 a and summarized performance results. The fluid loss testing exhibit excellent fluid loss control as well as an acceptable thickening time for the application of cementing operations for hydrocarbon wells even at elevated temperatures.

TABLE 11 Cementing fluid including first polymer 109a at elevated temperature Additive Quantity (grams) Water 239 Lime 10 First polymer 109a 212 Fluid loss additive 1.16 Dispersant 1.94 Low temperature retarder 5.45 Mid temperature retarder 5.45 Silica sand 272.65 Expansion additive 7.79 Cement 779 Fluid loss at BHST 51 mL Thickening Time at BHCT 23 Bc at 6 hours Settling No Free water 0

FIG. 4 is a flow chart of an example method 400 of forming a drilling fluid that includes a polymer-based latex, such as the cementing fluid 109 including the first polymer 109 a, the second polymer 109 b, or a mixture of both. At block 402, a first polymer (such as the first polymer 109 a) is formed. The first polymer 109 a formed at block 402 includes polyvinyl alcohol and polyvinyl acetate. Forming the first polymer 109 a at block 402 includes mixing calcium hydroxide and water to form a first mixture. Forming the first polymer 109 a at block 402 includes adding polyvinyl acetate to the first mixture to form a second mixture. Forming the first polymer 109 a at block 402 includes stirring the second mixture for a first specified time duration sufficient to hydrolyze at least a portion of the polyvinyl acetate into polyvinyl alcohol and form the first polymer 109 a. A molar concentration of the polyvinyl alcohol in the first polymer 109 a formed at block 402 is greater than 80% and less than 100% (for example, in a range of from about 80% to about 90%, from about 85% to about 95%, or from about 85% to about 90%). In some implementations, the first specified time duration is about 5 minutes. At block 404, a second polymer (such as the second polymer 109 b) is formed. Forming the second polymer 109 b at block 404 includes mixing citric acid and water to form a third mixture. Forming the second polymer 109 b at block 404 includes adding a styrene-butadiene polymer to the third mixture to form a fourth mixture. Forming the second polymer 109 b at block 404 includes stirring the fourth mixture for a second specified time duration sufficient for carboxylation of the styrene-butadiene to occur and form the second polymer 109 b. In some implementations, the second specified time duration is about 5 minutes. The second polymer 109 b formed at block 404 has the following general structure:

where x is an overall molar ratio of styrene in the second polymer 109 b, y is an overall molar ratio of butadiene in the second polymer 109 b, and z is an overall molar ratio of carboxylic acid in the second polymer 109 b. A sum of x, y, and z can be represented as s. In some implementations, x (styrene) is in a range of from about 20% to about 30% of s. In some implementations, y (butadiene) is in a range of from about 70% to about 80% of s. In some implementations, z (carboxylic acid) is in a range of from about 1% to about 5% of s. In some implementations, a ratio of x (styrene) to y (butadiene) in the second polymer 109 b is in a range of from about 0.22:1 to about 1:0.22. At block 406, the first polymer 109 a (formed at block 402) and the second polymer 109 b (formed at block 404) are mixed with an additive to form a drilling fluid (such as the cementing fluid 109). In some implementations, the additive mixed with the first polymer 109 a and the second polymer 109 b at block 406 to form the cementing fluid 109 includes at least one of starch, cellulosic polymer, dispersant, set retarder, silica, or an expanding additive. In some implementations, a molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 formed at block 406 is in a range of from about 1:2 to about 2:1. For example, the molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 formed at block 406 is about 1:1. In some implementations, a combined concentration of the first polymer 109 a and the second polymer 109 b in the cementing fluid 109 formed at block 406 is in a range of from about 0.1 volume percent (vol. %) to about 10 vol. %. For example, the combined concentration of the first polymer 109 a and the second polymer 109 b in the cementing fluid 109 formed at block 406 can be in a range of from about 2.4 vol. % to about 4.8 vol. %.

FIG. 5 is a flow chart of an example method 500 of drilling a wellbore in a subterranean formation. As an example, the rig system 100 can be used to implement the method 500. At block 502, a cementing fluid (such as the cementing fluid 109) is flowed through a tubular placed within a wellbore (for example, a casing that has been installed in the wellbore after the wellbore has been drilled). The cementing fluid 109 includes a latex. The latex can include a first polymer (such as the first polymer 109 a), a second polymer (such as the second polymer 109 b), or a mixture of both. The first polymer 109 a includes polyvinyl alcohol and polyvinyl acetate. In some implementations, a molar concentration of the polyvinyl alcohol in the first polymer 109 a is greater than 80% and less than 100% (for example, in a range of from about 80% to about 90%, from about 85% to about 95%, or from about 85% to about 90%). The second polymer 109 b is derived from styrene, butadiene, and a carboxylic acid. The second polymer 109 b has the following general structure:

where x is an overall molar ratio of styrene in the second polymer 109 b, y is an overall molar ratio of butadiene in the second polymer 109 b, and z is an overall molar ratio of carboxylic acid in the second polymer 109 b. A sum of x, y, and z can be represented as s. In some implementations, x (styrene) is in a range of from about 20% to about 30% of s. In some implementations, y (butadiene) is in a range of from about 70% to about 80% of s. In some implementations, z (carboxylic acid) is in a range of from about 1% to about 5% of s. In some implementations, a ratio of x (styrene) to y (butadiene) in the second polymer 109 b is in a range of from about 0.22:1 to about 1:0.22. In some implementations, the cementing fluid 109 includes an additive that includes at least one of starch, cellulosic polymer, dispersant, set retarder, silica, or an expanding additive. In some implementations, a molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 is in a range of from about 1:2 to about 2:1. For example, the molar ratio of the first polymer 109 a to the second polymer 109 b in the cementing fluid 109 is about 1:1. In some implementations, a combined concentration of the first polymer 109 a and the second polymer 109 b in the cementing fluid 109 is in a range of from about 0.1 volume percent (vol. %) to about 10 vol. %. For example, the combined concentration of the first polymer 109 a and the second polymer 109 b in the cementing fluid 109 can be in a range of from about 2.4 vol. % to about 4.8 vol. %. At block 504, a displacement fluid (for example, water) is flowed through the tubular, thereby displacing the cementing fluid 109 to at least partially fill an annular space defined between the tubular and the wellbore. At block 506, the cementing fluid 109 is allowed to harden in the annular space defined between the tubular and the wellbore. Allowing the cementing fluid 109 to harden in the annular space at block 506 cements the well.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of what may be claimed, but rather as descriptions of features that may be specific to particular implementations. Certain features that are described in this specification in the context of separate implementations can also be implemented, in combination, in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations, separately, or in any sub-combination. Moreover, although previously described features may be described as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can, in some cases, be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

As used in this disclosure, the terms “a,” “an,” or “the” are used to include one or more than one unless the context clearly dictates otherwise. The term “or” is used to refer to a nonexclusive “or” unless otherwise indicated. The statement “at least one of A and B” has the same meaning as “A, B, or A and B.” In addition, it is to be understood that the phraseology or terminology employed in this disclosure, and not otherwise defined, is for the purpose of description only and not of limitation. Any use of section headings is intended to aid reading of the document and is not to be interpreted as limiting; information that is relevant to a section heading may occur within or outside of that particular section.

As used in this disclosure, the term “about” or “approximately” can allow for a degree of variability in a value or range, for example, within 10%, within 5%, or within 1% of a stated value or of a stated limit of a range.

As used in this disclosure, the term “substantially” refers to a majority of, or mostly, as in at least about 50%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, 99.99%, or at least about 99.999% or more.

Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but also to include all the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range of “0.1% to about 5%” or “0.1% to 5%” should be interpreted to include about 0.1% to about 5%, as well as the individual values (for example, 1%, 2%, 3%, and 4%) and the sub-ranges (for example, 0.1% to 0.5%, 1.1% to 2.2%, 3.3% to 4.4%) within the indicated range. The statement “X to Y” has the same meaning as “about X to about Y,” unless indicated otherwise. Likewise, the statement “X, Y, or Z” has the same meaning as “about X, about Y, or about Z,” unless indicated otherwise.

Particular implementations of the subject matter have been described. Other implementations, alterations, and permutations of the described implementations are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results. In certain circumstances, multitasking or parallel processing (or a combination of multitasking and parallel processing) may be advantageous and performed as deemed appropriate.

Moreover, the separation or integration of various system modules and components in the previously described implementations should not be understood as requiring such separation or integration in all implementations, and it should be understood that the described components and systems can generally be integrated together or packaged into multiple products.

Accordingly, the previously described example implementations do not define or constrain the present disclosure. Other changes, substitutions, and alterations are also possible without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A cementing fluid composition comprising: a latex comprising a first polymer and a second polymer dispersed in water, wherein: the first polymer comprises polyvinyl alcohol and polyvinyl acetate, wherein a molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%; and the second polymer is derived from styrene, butadiene, and a carboxylic acid and has the general structure:

wherein: a sum of x, y, and z is equal to s, x is in a range of from about 20% to about 30% of s, y is in a range of from about 70% to about 80% of s, and z is in a range of from about 1% to about 5% of s; and a cement comprising calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and gypsum, wherein a concentration of the cement in the cementing fluid composition is in a range of from about 50 weight percent (wt. %) to about 80 wt. %, and a concentration of the latex in the cementing fluid composition is in a range of from about 1 wt. % to about 15 wt. %.
 2. The cementing fluid composition of claim 1, comprising an additive comprising at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive.
 3. The cementing fluid composition of claim 2, wherein a molar ratio of the first polymer to the second polymer in the cementing fluid composition is about 1:1.
 4. The cementing fluid composition of claim 3, wherein the molar concentration of the polyvinyl alcohol in the first polymer is about 88%.
 5. A method comprising: forming a first polymer comprising polyvinyl alcohol and polyvinyl acetate, wherein forming the first polymer comprises: mixing calcium hydroxide and water to form a first mixture; adding polyvinyl acetate to the first mixture to form a second mixture; and stirring the second mixture for a first specified time duration sufficient to hydrolyze at least a portion of the polyvinyl acetate into polyvinyl alcohol and form the first polymer, wherein a molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%; forming a second polymer, wherein forming the second polymer comprises: mixing citric acid and water to form a third mixture; adding a styrene-butadiene polymer to form a fourth mixture; and stirring the fourth mixture for a second specified time duration sufficient for carboxylation of the styrene-butadiene to occur and form the second polymer, wherein the second polymer has the general structure:

wherein: a sum of x, y, and z is equal to s, x is in a range of from about 20% to about 30% of s, y is in a range of from about 70% to about 80% of s, and z is in a range of from about 1% to about 5% of s; and mixing the first polymer and the second polymer with a cement to form a cementing fluid.
 6. The method of claim 5, wherein the additive comprises at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive.
 7. The method of claim 6, wherein a molar ratio of the first polymer to the second polymer in the cementing fluid is about 1:1.
 8. The method of claim 7, wherein a concentration of the cement in the cementing fluid is in a range of from about 50 weight percent (wt. %) to about 80 wt. %.
 9. The method of claim 8, wherein a combined concentration of the first polymer and the second polymer in the cementing fluid is in a range of from about 1 wt. % to about 15 wt. %.
 10. The method of claim 9, wherein the molar concentration of the polyvinyl alcohol in the first polymer is about 88%.
 11. A method comprising: flowing a cementing fluid through a tubular placed within a wellbore formed in a subterranean formation, wherein the cementing fluid comprises a cement and a latex comprising a first polymer and a second polymer, wherein: the first polymer comprises polyvinyl alcohol and polyvinyl acetate, wherein a molar concentration of the polyvinyl alcohol in the first polymer is greater than 80% and less than 100%; and the second polymer is derived from styrene, butadiene, and a carboxylic acid and has the general structure:

wherein: a sum of x, y, and z is equal to s, x is in a range of from about 20% to about 30% of s, y is in a range of from about 70% to about 80% of s, and z is in a range of from about 1% to about 5% of s; flowing a displacement fluid through the tubular, thereby displacing the cementing fluid to at least partially fill an annular space defined between the tubular and the wellbore; and allowing the cementing fluid to harden in the annular space defined between the tubular and the wellbore.
 12. The method of claim 11, wherein the cement comprises calcium oxide, silicon dioxide, aluminum oxide, iron oxide, and gypsum, and a concentration of the cement in the cementing fluid is in a range of from about 50 weight percent (wt. %) to about 80 wt. %.
 13. The method of claim 12, wherein a concentration of the latex in the cementing fluid is in a range of from about 1 wt. % to about 15 wt. %.
 14. The method of claim 13, wherein the cementing fluid comprises an additive comprising at least one of a starch, a cellulosic polymer, a dispersant, a set retarder, silica, or an expanding additive.
 15. The method of claim 14, wherein a molar ratio of the first polymer to the second polymer in the cementing fluid is about 1:1.
 16. The method of claim 15, wherein the molar concentration of the polyvinyl alcohol in the first polymer is about 88%. 